The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
H.264/AVC is the latest video compression standard, and is developed by JVT (Joint Video Team) formed of MPEG (Moving Picture Experts Group) and VCEG (Video coding Experts Group). H.264/AVC improves a compression rate 2 times greater than MPEG-2, and 1.5 times greater than MPEG-ASP (Advanced Simple Profile) using technologies such as intra-prediction, ¼ unit-based variable block size motion estimation/compensation, entropy encoding such as CAVLC (Context-adaptive variable-length coding) and CABAC (Context-adaptive binary arithmetic coding), and the like.
Among the technologies of H.264/AVC, the intra-prediction coding that is used for removing the spatial similarity of an image may perform prediction/compensation on a pixel value of a current block to be encoded, using a neighboring pixel that is already encoded as illustrated in FIG. 1. This method has been developed based on the idea in which spatially neighboring pixel values have a high correlation or high similarity to each other.
For more improving the efficiency of the intra-prediction, a possible method is to perform adaptive filtering on a predicted image which underwent the intra-prediction. The method may generate the intra-predicted image to be more natural by performing low-pass filtering on the intra-predicted image and thus, the compression efficiency may be improved. When the low-pass filtering is applied to an intra-predicted image that includes a clear directional edge, the blurring artifact may occur to blur the intra-predicted image, which will rather deteriorate the prediction efficiency. To overcome this, a filtering mode for the intra-predicted image may be used as illustrated in FIG. 2, so that whether to use a low-pass filter may be adaptively determined for each intra-predicted block and the problem may be settled. In this case, however, since the filtering mode will need to be transmitted for each intra-predicted block, the encoding efficiency generally deteriorates in the case of a video dominated by prediction images requiring no filtering.